[Dovecot] Problems with POP3 UIDL when migrating from MBOX to Maildir

[Joshua Goodall]

On Mon, Feb 13, 2006 at 11:22:26AM +1100, grant beattie wrote:
> the only side effect of using this feature is that you need to leave
> it turned on, even after users have POP'd into their mailbox because
> if you turn it off and are using an X-UIDL format such as the default,
> Dovecot knows that it can generate it on the fly and does so, even if
> the X-UIDL for a given message is present in the index.
> 
> the upshot of this is that every (new) message in a mailbox is read on
> each pop3 connection, looking for an X-UIDL header (that won't be
> there), resulting in higher disk IO than necessary.
> 
> I need to hack on the code to always use the X-UIDL from the index if
> present, then turn off pop3_reuse_xuidl and eliminate a bunch of
> disk IO.

That optimisation may be unnecessary: the common case is going to
be that new messages will be read, indexed, downloaded in one go.
It'll all be in buffer cache for that time so I wouldn't expect any
additional I/O on a sane OS; just more syscalls by Dovecot to get
the data.

In particular, no extra disk seek (which is what kills us).  Although
I confess I'm thinking mostly of maildirs here.

/k


-- 
Josh "Koshua" Goodall                      "as modern as tomorrow afternoon"
joshua at roughtrade.net                                       - FW109